The invention relates to a process for the preparation of polypeptides having a carboxamide carboxyl terminal end, to new peptides of this class, and to gene structures, plasmids and host organisms suitable for this purpose.
The direct synthesis of polypeptides having a carboxamide carboxyl terminal end by genetic engineering methods is not possible. However, a large number of natural peptides having a carboxamide terminal end have been isolated, such as PHI, VIP, CRF, nerve growth factor, oxytocin, cholecystokinin, gastrin, calcitonin, vasopressin, mellitin, melanotropin and, in particular, the growth hormone releasing factor, called "GRF" in the following text. The invention particularly relates to the preparation of peptides having the aminoacid sequence of GRF and of modified peptides similar to GRF, and of part sequences of these peptides. For this reason, in the following text, first the nature of the invention is illustrated by the preparation of peptides having the aminoacid sequence of GRF and of modified GRF derivatives: